Splice joint for plastic coated fabric conveyor belt and method of making the same

ABSTRACT

An apparatus and method for forming a splice in a conveyor belt. The apparatus includes a lower plate having a heating strip where the splice is being formed. The lower plate includes areas of insulation adjacent the heating strip to reduce transfer of heat to areas of the conveyor belt adjacent the splice during vulcanization or heating.

[0001] This application is a division of application Ser. No.09/307,543, filed May 7, 1999, now U.S. Pat. No. 6,321,903, whichclaimed the benefit of U.S. provisional application serial No.60/084,851, filed May 8, 1998. Application Ser. Nos. 09/307,543 and60/084,851 are hereby incorporated by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The present invention relates generally to new and novelimprovements in a splice joint for plastic coated fabric conveyor beltand method of making the same. More particularly, the present inventionrelates to a splice joint for plastic coated fabric conveyor belts andmethod of making the same which is particularly suitable for use inmachines that fabricate metal can lids.

[0003] Machines that fabricate metal can lids typically include acontinuous conveyor belt to transport and position the metal can lidmaterial during the metal can lid fabrication process. While it would bebeneficial to utilize an endless conveyor belt for the continuousconveyor belt in such metal can lid fabricating machines, the design ofmost metal can lid fabricating machines precludes the use of an endlessconveyor belt. In particular, most metal can lid fabricating machinesrequire a conveyor belt to be threaded through the metal can lidfabricating machine around pulleys therein and the two free conveyorbelt ends to be brought together and joined together to form a splicedcontinuous conveyor belt.

[0004] Spliced continuous conveyor belts used in metal can lidfabricating machines are sometimes fabricated by joining the two freeconveyor belt ends with a straight butt splice joint, often cut at anangle to increase the surface area of the splice joint. Another knownprior art method of joining the two free conveyor belt ends involvescutting the two free conveyor belt ends into a configuration commonlyreferred to as a “finger” type splice. In this configuration, the twoconveyor belt ends are typically overlapped and sheared or cut in amatched wavy or “finger” pattern. Such a “finger” type splice can beseen in U.S. Pat. No. 5,342,250 to Sanders for a “Process for theManufacture of an Endless Transfer Belt.” After shearing or cutting thetwo conveyor belt ends into a matched wavy or “finger” pattern, theconveyor belt is threaded through the metal can lid fabricating machineand the two conveyor belt ends are abutted together and melted to form acontinuous spliced conveyor belt. Pre-cut holes or pockets in theconveyor belt transport the metal can lid materials through the metalcan lid fabricating machines through various forming operations tofabricate metal can lids having the desired configuration.

[0005] Conveyor belts used in metal can lid fabricating machines areoften subjected to high levels of tension and stress due to the highspeeds at which conveyor belts are driven around the pulleys in typicalmetal can lid fabricating machines. This may cause conventional splicedcontinuous conveyor belts to tear, stretch or separate in the vicinityof the splice during normal operating conditions. Since most metal canlid fabricating machines require precise positioning of the metal canlid materials to fabricate metal can lids having the desiredconfiguration, any deviation in the length of the spliced continuousconveyor belt could be detrimental to the metal can lid fabricatingprocess.

[0006] In addition, vulcanizing (or heating) units used to heat knownprior art conveyor belts used in metal can lid fabricating machines havea broader than desired heating zone. Such vulcanizing units aregenerally multi-purpose units and are not designed for splicedcontinuous conveyor belts having lengths which are fabricated to closedimensional tolerances. Such a broad heating zone tends to deform theconveyor belt and affect the positioning of precision cut drive holeswhich are pre-punched into the conveyor belt. Deformation of these areascan result in misalignment of the metal can lid materials in the formingprocess and significant reduction of the service life expectancy of theconveyor belt. Thus, it is generally desirable to position the splicebetween the “holed” areas of the conveyor belt to shield the drive holesfrom heat from the vulcanizer unit.

[0007] In the shearing or cutting process used to fabricate splicedcontinuous conveyor belts for metal can lid fabricating machines, a pairof sharp shearing or cutting blades, including an upper shearing orcutting blade and a lower shearing or cutting blade, are brought intoclose proximity to one another. The conveyor belting material, which ispositioned between the shearing or cutting blades, is sheared or cut bythe combination of the force applied by the shearing or cutting blades,the hardness of the shearing or cutting blades and the sharpness of theshearing or cutting blade edges. If more than one layer of material liesbetween the shearing or cutting blades and the upper shearing or cuttingblade is brought down towards the lower shearing or cutting blade, thebottom layer of the material becomes the lower shearing plane for theupper layer of material. Since the lower layer of material does not havethe hardness and sharpness characteristics of a shearing or cuttingblade, it will tend to compress, flow and distort the cut edges of boththe upper and the lower material layers.

[0008] Vulcanization is a term used to describe the process of joiningrubber and/or plastic materials together by heating the materials underan applied pressure in a confined environment to cause the particles inthe materials being joined to flow and intermix with each other. As thetemperature is reduced, the materials cool and the particles curetogether to form a solid bond. In utilizing this process to fabricate acontinuous spliced conveyor belt having a straight butt splice joint ora “finger” type splice joint, the wavy or “finger” conveyor belt endstend to draw away from each other due to the pressure applied during thevulcanization or heating process. This drawing away of the conveyor beltends can result in less than desirable intermixing of the particlesduring the vulcanization process, thus forming a joint which is weakerthan desirable.

[0009] An object of the present invention is the provision of a splicejoint for plastic coated fabric conveyor belt or similar article whichutilizes a relatively narrow heat zone to vulcanize the two conveyorbelt ends to be joined together and shields the remainder of theconveyor belt from the heat used in the vulcanizing process.

[0010] A further object of the present invention is the provision of asplice joint for plastic coated fabric conveyor belt or similar articlewhich provides increased surface area on the two conveyor belt ends inthe splice joint zone to provide a stronger bond between the twoconveyor belt ends.

[0011] Yet another object of the present invention is the provision of asplice joint for plastic coated fabric conveyor belt or similar articlewhich provides for a stronger and more durable splice between the twoconveyor belt ends.

[0012] Yet a further object of the present invention is the provision ofa splice joint for plastic coated fabric conveyor belt or similararticle which provides better dimensional accuracy for a continuousspliced conveyor belt fabricated by joining two conveyor belt ends.

[0013] The foregoing and other aspects will become apparent from thefollowing detailed description of the invention when considered inconjunction with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a top view of an interlocked pair of representativeconveyor belt ends according to one embodiment of the present invention;

[0015]FIG. 2 is a top view of an interlocked pair of representativeconveyor belt ends according to a second embodiment of the presentinvention;

[0016]FIG. 3 is a top view of a lower insert plate used for vulcanizingthe conveyor belt ends together; and

[0017]FIG. 4 is a cross-sectional side view of the lower insert plateand a corresponding upper insert plate used for vulcanizing the conveyorbelt ends together.

DETAILED DESCRIPTION

[0018] Referring first to FIG. 1, which shows atop view of aninterlocked pair of representative conveyor belt ends, which utilizecorresponding male 18 and female 17 mushroom shapes to create aninterlocking splice joint in accordance with a first embodiment of asplice joint for plastic coated fabric conveyor belt. Continuous splicedconveyor belt 10 is formed by joining a matched pair of conveyor beltends 12 and 14 together. The conveyor belting material is preferably aplastic coated Kevlar® fabric material and is typically pre-cut byvarious methods to provide substantially equidistant conveyor belt driveholes 16 along the length of the conveyor belting material. Conveyorbelt drive holes 16 are utilized to both carry the metal can lidmaterial through the forming process and drive continuous splicedconveyor belt 10 around the internal pulleys of the metal can lidfabricating machine. When stamping conveyor belt drive holes 16 into theconveyor belting material, it is preferable that the conveyor beltingmaterial be placed under a tensile load during the conveyor belt drivehole shearing or cutting operation that is substantially equivalent tothe tensile load the continuous spliced conveyor belt will experienceduring normal usage. An alternative to this is to pre-cut conveyor beltdrive holes 16 in an out of round configuration, slightly wider alongtheir transverse axis than along their longitudinal axis and withconveyor belt drive holes 16 positioned slightly closer together alongtheir longitudinal axis, when the conveyor belt material is in anuntensioned or free condition, so conveyor belt drive holes 16 aresubstantially round and properly positioned relative to each other thencontinuous spliced conveyor belt 10 is placed under tension during use.

[0019] Referring next to FIG. 2, which shows a top view of aninterlocked pair of representative conveyor belt ends which utilizecorresponding male 27 and female 28 arrowhead shapes to create aninterlocking splice joint in accordance with a second embodiment of asplice joint for plastic coated fabric conveyor belt. Continuous splicedconveyor belt 20 is formed by joining a matched pair of conveyor beltends 22 and 24 together. The conveyor belting material is preferably aplastic coated Kevlar® fabric material and is typically pre-cut byvarious methods to provide substantially equidistant conveyor belt driveholes 26 along the length of the conveyor belting material. Conveyorbelt drive holes 26 are utilized to both carry the metal can lidmaterial through the forming process and drive continuous splicedconveyor belt 20 around the internal pulleys of the metal can lidfabricating machine.

[0020] When stamping conveyor belt drive holes 26 into the conveyorbelting material, it is preferable that the conveyor belting material beplaced under a tensile load during the conveyor belt drive hole shearingor cutting operation which is substantially equivalent to the tensileload the continuous spliced conveyor belt will experience during normalusage. An alternative to this is to pre-cut conveyor belt drive holes 26in an out of round configuration, slightly wider along their transverseaxis than along their longitudinal axis, and with conveyor belt driveholes 26 positioned slightly closer together along their longitudinalaxis, when the conveyor belt material is in an untensioned or freecondition so conveyor belt drive holes 26 are substantially round andproperly positioned relative to each other then continuous splicedconveyor belt 10 is placed under tension during use.

[0021] To form continuous spliced conveyor belts 10 and 20, one end ofthe conveyor belting material is placed inside the left side of ashearing or cutting apparatus over conveyor belt drive hole alignmentguides with the free end of the conveyor belting material projecting outof the shearing or cutting apparatus. This cutting or shearing operationcan be conducted at substantially the same time conveyor belt driveholes 16 or 26 are formed or, alternatively, as an independentoperation, preferably after conveyor belt drive holes 16 or 26 areformed. The configuration of the shearing or cutting blades correspondsto the configuration of the desired conveyor belt ends 12 and 14 or 22and 24. Once the conveyor belting material is properly positioned in theshearing or cutting apparatus, upper shearing or cutting blade and lowershearing or cutting blade are brought together under pressure. Beforethe shearing or cutting edges come into contact with the conveyorbelting material, a spring loaded pressure pad engages the conveyorbelting material adjacent to the shearing or cutting area to hold theconveyor belting material firmly in the desired position for shearing orcutting. A blanking style cut with zero (0) degrees of blade rake angleis preferred to prevent distortion of the shear or cut, although othertypes of shears or cuts could alternatively be used if desired. Theclearance between the upper shearing or cutting blade and the lowershearing or cutting blade is preferably set to be less than 0.001inches. As the upper shearing or cutting blade and the lower shearing orcutting blade engage the conveyor belting material, it is sheared or cutcleanly without a burred edge. Conveyor belt end 14 or 24 is then placedin the right side of the shearing or cutting apparatus and is alignedand sheared or cut in the same fashion as described above in connectionwith conveyor belt end 12 or 22. The end result of this conveyor beltend shearing or cutting process are two matching and opposed conveyorbelt ends 12 and 14 or 22 and 24.

[0022] Conveyor belting material is then threaded through the metal canlid fabricating machine around the interior pulleys and conveyor beltend 12 or 22 and conveyor belt end 14 or 24 are positioned in thevulcanization or heating area. The pulley tension of the metal can lidfabricating machine is preferably relaxed to provide slack in theconveyor belting material which enables temporary insertion of a lowerportion of a standard vulcanizing (or heating) unit for the joiningprocess. Referring to FIGS. 3 and 4, a lower insert plate 30 and acorresponding upper insert plate 40 utilize pin tooling and edge guidesto properly align and contain the interlocking splice joint duringvulcanization. Lower heat resistant insert plate 30 is placed on top ofthe heating surface of the lower portion of the vulcanizer unit (notshown). Conveyor belt end 12 or 22 is then placed over the appropriateprojections 32 on the left side of lower heat resistant insert plate 30and conveyor belt end 14 or 24 is placed over appropriate projections 34on the right side of the lower heat resistant insert plate 30. Conveyorbelt end 12 or 22 and conveyor belt end 14 or 24 are thus mechanicallylocked in both edge to edge alignment and center to center alignmentwith a contoured heating strip 37 being positioned directly below thesplicing area. Insulative material 36 is preferably provided in lowerheat resistant insert plate 30 to preclude and minimize heat transferfrom the vulcanizer unit to continuous spliced conveyor belt 10 or 20except in the vicinity of the splice joint to preclude and minimizeexcessive distortion of continuous spliced conveyor belt 10 or 20 in thevicinity of the splice joint. An adhesive may be applied to the face ofconveyor belt end 12 or 22 and conveyor belt end 14 or 24, if desired ornecessary to create the desired cure between conveyor belt end 12 or 22and conveyor belt end 14 or 24.

[0023] It should be recognized that other shapes for the contouredheating strip could alternatively be utilized to fabricate continuousspliced conveyor belt 10 or 20. In general, a particular shape for thecontoured heating strip is chosen by weighted comparisons of the cost toproduce the configuration with the overall effectiveness of differentconfigurations. The shape of contoured heating strip is preferablysubstantially the same as the configuration of conveyor belt end 12 or22 and conveyor belt 14 or 24 and is slightly larger than the splicearea.

[0024] To reduce the possibility of the splice joint splitting ortearing from wear and tension as continuous spliced conveyor belt 10 or20 travel over pulleys in the metal can lid fabricating machine, theshape of the splice cut can be modified, if desired, to incorporate astaggered “S” shape, as shown in FIG. 2, which positions the splicejoint in front of one conveyor belt drive hole 16 or 26 and behind theadjacent conveyor belt drive hole 16 or 26. Thus, as the drive pins onthe metal can lid fabricating machine's pulleys enter conveyor beltdrive holes 16 or 26, the staggered “S” shaped splice joint precludes orminimizes back tension from simultaneously pulling across the entirelength of the splice joint. The staggered “S” shape also allows forgreater spacing between the splice joint and conveyor belt drive holes16 or 26 than a straight bias cut would provide. Furthermore, thestaggered “S” shape provides a curve at each end of the splice joint asit approaches the outer and inner edges of continuous spliced conveyorbelt 10 or 20 that is primarily oriented in a direction opposite to thedirection of conveyor belt travel. Providing a curve at the ends of thesplice joint that is primarily oriented in a direction opposite to thedirection of conveyor belt travel reduces the possibility of the splicejoint in continuous spliced conveyor belt 10 or 20 splitting or becomingseparated at the edges of the continuous conveyor belt; a problem thatis commonly associated with traditional straight butt and finger typesplice joints. The curvature at the ends of the splice joint alsoprecludes or minimizes a catch point that is created by traditionalfinger type splice joints that come to a sharp point at one or moreedges of the continuous conveyor belt, which tend to peel during use.One other advantage of having curvature at the ends of the splice jointis that the splice joint is positioned further from conveyor belt driveholes 16 and 26, which significantly reduces the linear stress at theends of the splice joint.

[0025] Upper heat resistant insert plate 40 is then inserted onto thetop surface of the conveyor belting material. Projections 48 downwardlyextending from the bottom of upper heat resistant insert plate 40 arepositioned firmly inside the top half of conveyor belt drive holes 16 or26 to properly position upper heat resistant insert plate 40 along thelength of the splice joint. Locating pins 42 downwardly extending fromupper heat resistant insert plate 40 correspond with openings 44 inlower heat resistant insert plate 30 to provide accurate positioning oflower heat resistant insert plate 30 and upper heat resistant insertplate 40 over and under continuous spliced conveyor belt 10 or 20. Edgeguides 46 upwardly extending from lower heat resistant insert plate 30align and contain the edges of continuous spliced conveyor belt 10 or 20and preclude or minimize melted plastic from extruding out of the splicejoint area.

[0026] The top portion of the vulcanizer unit (not shown) is then placedon top of upper heat resistant insert plate 40 and the top and bottomportions of the vulcanizer unit are fastened together. The vulcanizerunit is then pressurized, typically with air, to further sandwich andposition conveyor belt end 12 or 22 and conveyor belt end 14 or 24. Heatis then applied to the heat strips by the vulcanizer unit and conveyorbelt end 12 or 22 and conveyor belt end 14 or 24 heat up to atemperature of, for example, approximately 350° F. and their particlesintermix. As heat is removed, the conveyor belt splice joint area coolsand conveyor belt end 12 or 22 and conveyor belt end 14 or 24 cure toform a strong chemical bond therebetween. The vulcanizer unit and theheat plates are then removed from conveyor belt end 12 or 22 andconveyor belt end 14 and 24, thus forming continuous spliced conveyorbelt 10 or 20 having good dimensional accuracy for both edge to edgealignment and conveyor belt drive hole 16 or 26 to conveyor belt drivehole 16 or 26 distance over the conveyor belt splice joint area. Inaddition, conveyor belt drive holes 16 or 26 near the conveyor beltsplice joint area are not distorted and the conveyor belt splice area issubstantially imperceptible in relation to the remainder of continuousspliced conveyor belt 10 or 20.

[0027] Since the conveyor belt splice joint area inherently has theweakest tensile strength of a properly manufactured continuous splicedconveyor belt, it is also the area most prone to stress induced failure.Thus, improving the tensile strength of the conveyor belt splice jointarea increases the service life expectancy of the continuous splicedconveyor belt, which in turn improves productivity and profitability byreducing metal can lid fabricating machine downtime, as well as wear andtear on the forming dies and the internal components of metal can lidfabricating machines.

[0028] Accordingly, although the present invention has been describedabove in detail, the same is by way of illustration and example only andis not to be taken as a limitation on the present invention. Forexample, rather than utilizing corresponding male and female mushroomshapes or arrow-head shapes for the “jig-saw puzzle” type splice joint,other configurations could alternatively be used. In addition, one sideof the conveyor belt end could include all male projections and theother conveyor belt end could include all female sockets if desired.Thus, it is apparent to those having a level of ordinary skill in therelevant art that other variations and modifications in the constructionof the splice joint for plastic coated fabric conveyor belt or similararticle and method of making the same could be readily made using theteachings of the present invention. Accordingly, the scope and contentof the present invention are to be defined only by the terms of theappended claims.

What is claimed is:
 1. An apparatus for forming a splice in a conveyorbelt, the conveyor belt having two ends, the apparatus comprising: alower guide plate holding one end of the conveyor belt in a firstpredetermined position, and holding the other end of the conveyor beltin a second predetermined position, the lower guide plate having aheating strip therein, the ends of the conveyor belt being positionedover the heating strip; and an upper guide plate matingly engaging thelower guide plate to hold the ends of the conveyor belt in thepredetermined positions, the lower guide plate and the upper guide plateincluding a plurality of areas of insulative material adjacent theheating strip, the areas of insulative material reducing the transfer ofheat from the heating strip to portions of the conveyor belt adjacentthe conveyor belt ends.
 2. The apparatus according to claim 1, whereinthe ends of the conveyor belt have a curvilinear shape and the heatingstrip has a corresponding curvilinear shape.
 3. The apparatus accordingto claim 2, wherein the curvilinear shape is a staggered S-shape.
 4. Theapparatus according to claim 1, wherein the conveyor belt has aplurality of apertures therein and at least one of the lower guide plateand the upper guide plate has plurality of conveyor belt apertureengaging projections thereon.
 5. The apparatus according to claim 4,wherein at least one conveyor belt aperture engaging projection has anaperture therein and at least one conveyor belt aperture engagingprojection has a corresponding pin extending therefrom.
 6. The apparatusaccording to claim 4, wherein the insulative material is also positionedabout the conveyor belt aperture engaging projections.
 7. The apparatusaccording to claim 1, wherein the conveyor belt has a plurality ofapertures therein and the lower guide plate and the upper guide plateeach have a plurality of conveyor belt aperture engaging projectionsthereon.
 8. The apparatus according to claim 1, wherein the lower guideplate has an edge guide along each side thereof.
 9. An apparatus forforming a splice in a conveyor belt, the conveyor belt having aplurality of apertures therein and having two ends, the ends of theconveyor belt having a staggered S-shaped, the apparatus comprising: alower guide plate holding one end of the conveyor belt in a firstpredetermined position, and holding the other end of the conveyor beltin a second predetermined position, the lower guide plate having aheating strip therein, the ends of the conveyor belt being positionedover the heating strip; and an upper guide plate matingly engaging thelower guide plate to hold the ends of the conveyor belt in thepredetermined positions, the lower guide plate and the upper guide plateeach having a plurality of conveyor belt aperture engaging projectionsthereon and each including a plurality of areas of insulative materialadjacent the heating strip and about the conveyor belt aperture engagingprojections, the areas of insulative material reducing the transfer ofheat from the heating strip to portions of the conveyor belt adjacentthe conveyor belt ends.
 11. The apparatus according to claim 10, whereinat least one conveyor belt aperture engaging projection has an aperturetherein and at least one conveyor belt engaging projection has acorresponding pin extending therefrom.
 12. An apparatus for forming asplice in a conveyor belt, the conveyor belt having two ends, theapparatus comprising: a lower plate, the lower plate having a heatingstrip therein, the ends of the conveyor belt being positioned over theheating strip; and an upper plate engaging the lower plate, the lowerplate and the upper plate including a plurality of areas of Insulativematerial adjacent the heating strip, the areas of insulative materialreducing the transfer of heat from the heating strip to portions of theconveyor belt adjacent the conveyor belt ends.
 13. The apparatusaccording to claim 12, wherein the ends of the conveyor belt have acurvilinear shape and the heating strip has a corresponding curvilinearshape.
 14. The apparatus according to claim 12, wherein the curvilinearshape is a staggered S-shape.
 15. A method of forming a continuousspliced conveyor belt, comprising the steps of: cutting a first end of aconveyor belt material; cutting a second end of the conveyor beltmaterial; positioning the ends of the conveyor belt material adjacentone another; heating the ends of the conveyor belt material to join theends of the conveyor belt material together; and simultaneously with thestep of heating, insulating areas of the conveyor belt material adjacentthe ends of the conveyor belt material to reduce the transfer of heatfrom heated ends of the conveyor belt material.
 16. The method accordingto claim 15, wherein the steps of heating and insulating compriseproviding a lower plate having a heating strip therein and having aplurality of areas of insulative material adjacent the heating strip.17. The method according to claim 15, wherein the conveyor belt materialhas a plurality of apertures therein and the step of positioningincludes gripping the apertures preventing movement of the ends of theconveyor belt material relative to one another.
 18. The method accordingto claim 15, wherein the conveyor belt material has a plurality ofapertures therein and the step of positioning includes positioning theconveyor belt material such that none of the conveyor belt materialapertures directly heated during the step of heating.